Implicit Flutter Animations

Oct 4 2022 Dart 2.17, Flutter 3.0, Visual Studio Code 1.7

Part 2: Implicit Animations in Action

8. Create a Multi-Selection Animation

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Previous episode: 7. Create a Card Flip Animation Next episode: 9. Animate an Item Switcher

The student materials have been reviewed and are updated as of August 2022.

The updated material uses null safety and also deploys the use coding practises encouraged by the Flutter as per the Flutter lint rules and a few addons of practises that are considered good here at raywenderlich (see analysis_options.yaml in the material for more info).

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So far, we’ve seen how to select and animate a sigle item. In this episode, we would learn how to create a multi selection animation. This is a common feature in many apps and we would cover both the setup and the animation.

class ExtraItem extends StatefulWidget {
  final Extra extra;
  final ValueChanged<bool> onSelected;

  const ExtraItem({Key? key, required this.extra, required this.onSelected}) : super(key: key);
...

class _ExtraItemState extends State<ExtraItem> {
    bool _isSelected = false;
    @override
    Widget build(BuildContext context) {
        return InkWell(
            onTap: () {
                setState(() {
                    _isSelected = !_isSelected;
                    widget.onSelected(_isSelected);
                });
            },
            child: Container(
                ...

ExtraItem(
    extra: extras[i],
    onSelected: (bool value) {
        if (value) {
            _selectedExtras.add(extras[i]);
        } else {
            _selectedExtras.remove(extras[i]);
        }
        setState(() {});
    },
)

child: Column(
    children: [
        AnimatedContainer(
            duration: const Duration(milliseconds: 500),
            padding: const EdgeInsets.all(24),
            decoration: BoxDecoration(
                shape: BoxShape.circle,
                border: _isSelected
                    ? Border.all(
                        color: colorScheme.secondary,
                        width: 2,
                        )
                    : null,
            ),
            child: Image.asset(
                ...
            ),
        ),
        AnimatedDefaultTextStyle(
            duration: const Duration(milliseconds: 500),
            style: TextStyle(
              color: Colors.black,
              fontWeight: _isSelected ? FontWeight.w600 : FontWeight.normal,
            ),
            child: Text(
              widget.extra.name,
            ),
        ),
    ],
),